demos: Refactored Demo class in cubepp Moved 'Demo' declaration to near the top of the file to avoid referencing problems.
demos: Refactored Demo class in cubepp
Moved 'Demo' declaration to near the top of the file to avoid referencing
problems.

Change-Id: I084231ada5683971baa073f1b761ac214fa02cfd

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers